The use of magnetic bearings in rotary machines such as centrifugal gas compressors is increasing. Magnetic bearings work on the principle of electromagnetism. The use of electromagnetism in centrifugal gas compressor bearings reduces or eliminates friction losses in centrifugal gas compressors.
Magnetic bearings in rotary machines are generally arranged with multiple windings or electric coils surrounding a shaft formed from a ferromagnetic material. Some magnetic bearings use a ferromagnetic lamination for the radial bearings and a ferromagnetic thrust disk or thrust collar for the thrust bearings. The windings or coils in a radial magnetic bearing radially surround the shaft and produce a magnetic field that tends to attract or repel the rotor shaft. The windings or coils in a thrust magnetic bearing produces a magnetic field that tends to attract or repel a thrust collar attached to the shaft to counteract axial forces. The attractive forces of the windings or coils may be controlled by varying the current in each winding or coil. Magnetic bearing thrust collars may require a larger outer diameter than the outer diameter of a mechanical bearing thrust collar to match the load capacity of the mechanical bearing thrust collar.
U.S. Pat. No. 4,948,348 to R. Doll discloses an immersion pump, especially for low-boiling fluids, having a support for a shaft and a ferromagnetic impeller wheel mounted to the shaft. The support includes at least one controllable electromagnet that operates to axially support and position the impeller wheel.
The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors.